Struct arrow::datatypes::Schema

pub struct Schema {
    pub fields: Fields,
    pub metadata: HashMap<String, String>,
}
Expand description

Describes the meta-data of an ordered sequence of relative types.

Note that this information is only part of the meta-data and not part of the physical memory layout.

Fields§

§fields: Fields§metadata: HashMap<String, String>

A map of key-value pairs containing additional meta data.

Implementations§

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impl Schema

pub fn empty() -> Schema

Creates an empty Schema

pub fn new(fields: impl Into<Fields>) -> Schema

Creates a new Schema from a sequence of Field values.

§Example
let field_a = Field::new("a", DataType::Int64, false);
let field_b = Field::new("b", DataType::Boolean, false);

let schema = Schema::new(vec![field_a, field_b]);

pub fn new_with_metadata( fields: impl Into<Fields>, metadata: HashMap<String, String>, ) -> Schema

Creates a new Schema from a sequence of Field values and adds additional metadata in form of key value pairs.

§Example

let field_a = Field::new("a", DataType::Int64, false);
let field_b = Field::new("b", DataType::Boolean, false);

let mut metadata: HashMap<String, String> = HashMap::new();
metadata.insert("row_count".to_string(), "100".to_string());

let schema = Schema::new_with_metadata(vec![field_a, field_b], metadata);

pub fn with_metadata(self, metadata: HashMap<String, String>) -> Schema

Sets the metadata of this Schema to be metadata and returns self

pub fn project(&self, indices: &[usize]) -> Result<Schema, ArrowError>

Returns a new schema with only the specified columns in the new schema This carries metadata from the parent schema over as well

pub fn try_merge( schemas: impl IntoIterator<Item = Schema>, ) -> Result<Schema, ArrowError>

Merge schema into self if it is compatible. Struct fields will be merged recursively.

Example:


let merged = Schema::try_merge(vec![
    Schema::new(vec![
        Field::new("c1", DataType::Int64, false),
        Field::new("c2", DataType::Utf8, false),
    ]),
    Schema::new(vec![
        Field::new("c1", DataType::Int64, true),
        Field::new("c2", DataType::Utf8, false),
        Field::new("c3", DataType::Utf8, false),
    ]),
]).unwrap();

assert_eq!(
    merged,
    Schema::new(vec![
        Field::new("c1", DataType::Int64, true),
        Field::new("c2", DataType::Utf8, false),
        Field::new("c3", DataType::Utf8, false),
    ]),
);

pub const fn fields(&self) -> &Fields

Returns an immutable reference of the vector of Field instances.

pub fn flattened_fields(&self) -> Vec<&Field>

Returns a vector with references to all fields (including nested fields)

§Example
use std::sync::Arc;
use arrow_schema::{DataType, Field, Fields, Schema};

let f1 = Arc::new(Field::new("a", DataType::Boolean, false));

let f2_inner = Arc::new(Field::new("b_inner", DataType::Int8, false));
let f2 = Arc::new(Field::new("b", DataType::List(f2_inner.clone()), false));

let f3_inner1 = Arc::new(Field::new("c_inner1", DataType::Int8, false));
let f3_inner2 = Arc::new(Field::new("c_inner2", DataType::Int8, false));
let f3 = Arc::new(Field::new(
    "c",
    DataType::Struct(vec![f3_inner1.clone(), f3_inner2.clone()].into()),
    false
));

let mut schema = Schema::new(vec![
  f1.clone(), f2.clone(), f3.clone()
]);
assert_eq!(
    schema.flattened_fields(),
    vec![
        f1.as_ref(),
        f2.as_ref(),
        f2_inner.as_ref(),
        f3.as_ref(),
        f3_inner1.as_ref(),
        f3_inner2.as_ref()
   ]
);

pub fn all_fields(&self) -> Vec<&Field>

👎Deprecated since 52.2.0: Use flattened_fields instead

Returns a vector with references to all fields (including nested fields)

pub fn field(&self, i: usize) -> &Field

Returns an immutable reference of a specific Field instance selected using an offset within the internal fields vector.

§Panics

Panics if index out of bounds

pub fn field_with_name(&self, name: &str) -> Result<&Field, ArrowError>

Returns an immutable reference of a specific Field instance selected by name.

pub fn fields_with_dict_id(&self, dict_id: i64) -> Vec<&Field>

Returns a vector of immutable references to all Field instances selected by the dictionary ID they use.

pub fn index_of(&self, name: &str) -> Result<usize, ArrowError>

Find the index of the column with the given name.

pub const fn metadata(&self) -> &HashMap<String, String>

Returns an immutable reference to the Map of custom metadata key-value pairs.

pub fn column_with_name(&self, name: &str) -> Option<(usize, &Field)>

Look up a column by name and return a immutable reference to the column along with its index.

pub fn contains(&self, other: &Schema) -> bool

Check to see if self is a superset of other schema.

In particular returns true if self.metadata is a superset of other.metadata and Fields::contains for self.fields and other.fields

In other words, any record that conforms to other should also conform to self.

Trait Implementations§

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impl Clone for Schema

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fn clone(&self) -> Schema

Returns a copy of the value. Read more
1.0.0 · source§

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl Debug for Schema

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fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter. Read more
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impl<'de> Deserialize<'de> for Schema

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fn deserialize<__D>( __deserializer: __D, ) -> Result<Schema, <__D as Deserializer<'de>>::Error>
where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer. Read more
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impl Display for Schema

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fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter. Read more
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impl From<&Schema> for SchemaBuilder

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fn from(value: &Schema) -> SchemaBuilder

Converts to this type from the input type.
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impl From<Schema> for SchemaBuilder

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fn from(value: Schema) -> SchemaBuilder

Converts to this type from the input type.
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impl FromPyArrow for Schema

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fn from_pyarrow_bound(value: &Bound<'_, PyAny>) -> PyResult<Self>

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fn from_pyarrow(value: &PyAny) -> PyResult<Self>

👎Deprecated since 52.0.0: Use from_pyarrow_bound
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impl Hash for Schema

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fn hash<H>(&self, state: &mut H)
where H: Hasher,

Feeds this value into the given Hasher. Read more
1.3.0 · source§

fn hash_slice<H>(data: &[Self], state: &mut H)
where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher. Read more
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impl PartialEq for Schema

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fn eq(&self, other: &Schema) -> bool

This method tests for self and other values to be equal, and is used by ==.
1.0.0 · source§

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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impl Serialize for Schema

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fn serialize<__S>( &self, __serializer: __S, ) -> Result<<__S as Serializer>::Ok, <__S as Serializer>::Error>
where __S: Serializer,

Serialize this value into the given Serde serializer. Read more
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impl ToPyArrow for Schema

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fn to_pyarrow(&self, py: Python<'_>) -> PyResult<PyObject>

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impl TryFrom<&FFI_ArrowSchema> for Schema

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type Error = ArrowError

The type returned in the event of a conversion error.
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fn try_from(c_schema: &FFI_ArrowSchema) -> Result<Schema, ArrowError>

Performs the conversion.
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impl TryFrom<&Schema> for FFI_ArrowSchema

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type Error = ArrowError

The type returned in the event of a conversion error.
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fn try_from(schema: &Schema) -> Result<FFI_ArrowSchema, ArrowError>

Performs the conversion.
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impl TryFrom<Schema> for FFI_ArrowSchema

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type Error = ArrowError

The type returned in the event of a conversion error.
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fn try_from(schema: Schema) -> Result<FFI_ArrowSchema, ArrowError>

Performs the conversion.
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impl Eq for Schema

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impl StructuralPartialEq for Schema

Auto Trait Implementations§

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impl Freeze for Schema

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impl RefUnwindSafe for Schema

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impl Send for Schema

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impl Sync for Schema

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impl Unpin for Schema

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impl UnwindSafe for Schema

Blanket Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> CloneToUninit for T
where T: Clone,

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default unsafe fn clone_to_uninit(&self, dst: *mut T)

🔬This is a nightly-only experimental API. (clone_to_uninit)
Performs copy-assignment from self to dst. Read more
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impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

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fn equivalent(&self, key: &K) -> bool

Checks if this value is equivalent to the given key. Read more
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impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

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fn equivalent(&self, key: &K) -> bool

Compare self to key and return true if they are equal.
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> IntoPyArrow for T
where T: ToPyArrow,

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fn into_pyarrow(self, py: Python<'_>) -> Result<Py<PyAny>, PyErr>

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impl<T> ToOwned for T
where T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T> ToString for T
where T: Display + ?Sized,

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default fn to_string(&self) -> String

Converts the given value to a String. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<V, T> VZip<V> for T
where V: MultiLane<T>,

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fn vzip(self) -> V

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impl<T> Allocation for T
where T: RefUnwindSafe + Send + Sync,

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impl<T> DeserializeOwned for T
where T: for<'de> Deserialize<'de>,

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impl<T> Ungil for T
where T: Send,